This invention relates to electric fuel pumps, and more particularly to an improved check valve for such pumps which eliminates noise or chattering in the pump and reduces warranty returns caused by complaints of such chattering or noise.
As shown in the sectional view of FIG. 1, in one type of prior art electric fuel pump construction, a check valve V is installed in a fuel pump to prevent backflow of fuel into the pump and maintain the pressure in the fuel system of which the pump is a component. As shown in the FIG., the check valve includes a hemispherically shaped valve member B attached to a pintle or stem P for reciprocal movement through an outlet passage O of the pump. A spring S encloses the pintle and the resultant assembly is installed in the outlet of the pump during its fabrication. When the pump is in operation, the pintle is forced away from its seat and fuel flows around a sealing surface of the pintle and out of the pump. Ideally, fluid flow around the pintle stabilizes the pintle and keeps it relatively stationary due to the equalized forces surrounding it. In actuality, this does not happen. Rather, the forces are not equal for a variety of reasons and the result is that the pintle fluctuates from side-to-side in the outlet, producing a discernible noise or chatter.
A different prior art construction is shown in FIG. 2. Here, a check valve V′ installed in the outlet passage O′ of a fuel pump, comprises a ball and a spring S′. A seat Y is pressed into the inlet end of the outlet for the ball to seat against and seal the passage. When the pump is running, the ball is forced away from its seat against the force of the spring, and fuel flows around the ball, through the passage, and out of the pump. When the pump is shut off, the spring and fuel system pressure forces the ball back against its seat preventing backflow of fuel into the pump while maintaining fuel system pressure. As with the prior art check valve of FIG. 1, during pump operation, the ball member fluctuates about in the passage, again producing a discernible noise or chatter.
People driving vehicles in which one of these prior art fuel pumps is installed often attribute the valve related noise to a malfunctioning of the pump and seek replacement of the pump. This results in a warranty return that requires the pump manufacturer to replace the pump, usually at no cost to the vehicle manufacturer, and so increases the cost of the pump to the manufacturer.